

uniform vec3  BrickColor, MortarColor; 
uniform vec2  BrickSize; 
uniform vec2  BrickPct; 
varying vec2  MCposition; 
varying float LightIntensity; 
void main() 
{ 
    vec3  color; 
    vec2  position, useBrick; 
    position = MCposition / BrickSize; 
    if (fract(position.y * 0.5) > 0.5) 
        position.x += 0.5; 
    position = fract(position); 
    useBrick = step(position, BrickPct); 
    color  = mix(MortarColor, BrickColor, useBrick.x * useBrick.y); 
    color *= LightIntensity; 
    gl_FragColor = vec4(color, 1.0); 
}
